Effect of Q-factor manipulation via pedal spacers on lower limb frontal plane kinematics during cycling

Anecdotal evidence suggests that frontal plane kinematics of the lower extremity are an important aspect of bicycle fit, however, frontal plane adjustments are often overlooked during common fitting procedures. The purpose of this study was to manipulate Q-factor width via pedal spacers to determine their influence on frontal plane kinematics of the hip, knee, and ankle during cycling. Twenty-four young healthy recreational cyclists (12 female) completed five minutes of pedaling at their preferred cadence and power output under three stance widths conditions: no spacer, 20 mm spacer, and 30 mm spacer. For each participant, the pedaling cadence and power output were kept identical for all experimental conditions. Lower extremity marker position data were captured at 250 Hz for the last two minutes of each condition. Sixty consecutive crank cycles were analyzed to identify maximum and minimum hip, knee, and ankle angles in the frontal plane. With an increase in Q-factor, hip and knee maximum abduction angles increased and maximum adduction angles decreased. With increase in Q-factor from no spacer to 20 mm spacer condition, hip abduction increased by 0.8o (∆10%; p<0.001) whereas hip abduction decreased by 0.9o (∆23%; p<0.001) and similarly, knee abduction increased by 1.2o (∆60%; p=0.002) whereas knee abduction decreased by 1.1o (∆18%; p=0.003). And with increase in Q-factor from no spacer to 30 mm spacer condition, hip abduction increased by 1.4o (∆18%; p<0.001) and hip adduction decreased by 1.6o (∆40%; p<0.001) and similarly, knee abduction increased by 1.8o (∆86%; p<0.001) and knee adduction decreased by 2.1o (∆35%; p<0.001). Maximum and minimum ankle angles were not affected by the stance width conditions (p>0.05). Pedal spacers are an effective way of manipulating Q-factor and frontal plane kinematics of the hip and knee and could help cyclists experiencing medial or lateral knee pain.